Method for realizing dynamic packet communication in Modbus RTU network

Abstract

The invention discloses a method for realizing dynamic packet communication in a Modbus RTU network. The method for realizing dynamic packet communication in the Modbus RTU network comprises the stepsthat a node address uses a Modbus standard 8-bit address, wherein the message format is completely compatible with a Modbus RTU specification; and the 8-bit address is divided into a grouping bit andan address bit, wherein the bit number of the grouping bit or the grouping mode can be set by a Modbus master node (master), and the value range is from 0 to 7. The method has the beneficial effectsthat the Modbus RTU standard does not support a multicast function, the prior art aiming at the problem has obvious defects, and the technologies are used for physically isolating the network at the hardware level to realize grouping or multiplying the 8-bit address of the Modbus RTU standard. The technologies cannot be compatible with the Modbus RTU standard, and are high in cost and poor in flexibility.

Description

technical field [0001] The invention relates to the field of Modbus, in particular to a method for realizing dynamic packet communication in a Modbus RTU network. Background technique [0002] The Modbus communication protocol is widely used in the field of automation control. Specifically, it is divided into three communication modes: Modbus ASCII, Modbus RTU and Modbus TCP, among which Modbus RTU is the most common in practical applications. Modbus RTU protocol is a serial protocol of master-slave (master / slave) architecture: in a ModBus network, it contains a master node (master) with address 0 and multiple slave nodes (slave), each slave device There is a unique address, and the address value is between 1 and 247. [0003] The Modbus RTU specification does not allow repeated node addresses, and the standard protocol does not have broadcast and multicast functions (the address of the communication protocol is one byte, indicating a certain node address). If the master n...

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Problems solved by technology

[0005] 1. The Modbus standard does not support broadcast and multicast functions. If the master node wants to send the same command to multiple slave nodes, it must be sent one by one.

[0006] 2. No dynamic packet communication technology compatible with the serial Modbus message format has been found in the standard Modbus RTU network

[0007] 3. Some extensions expand the automatic length of the address, which is not compatible with the serial Modbus standard (equivalent to formulating another standard)

[0008] 4. Part of the expansion technology uses hardware to isolate the network, but it is not implemented on the standard Modbus network, the flexibility is poor, and it is impossible to realize unicast, multicast and broadcast at the same time

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